I'd totally do it, but I'm single and horny, so... ;-) lol
Yes, I would accept sex in exchange for staying here and being under my protection.
There would have to be some kind of contract. I just think trading on the goodness of his word could too easily lead to abuse.
I'd hate to say it, but your question seems to describe most people's idea of marriage.
How good is the sex?
Nah not worth it